The team discovered that fish do this by binding the calcium to bicarbonate, and then excreting it as pellets of calcium carbonate, a chalk-like substance also known as "gut rocks," in a process completely separate from food digestion. For an animation of this process, visit www.publicaffairs.ubc.ca/download.

As the calcium carbonate from these pellets dissolves, it turns the seawater more alkaline, which has relevance for ocean acidification, and is impacted by the ocean's exchange of carbon dioxide (CO2) with the atmosphere.